The present invention relates to a semiconductor device, and more particular, to a semiconductor device having a charge pump circuit, for example.
In recent years, from the viewpoint of the protection of the environment, many energy harvesting techniques of harvesting electric power from environmental electric waves to operate circuits have been proposed. In this energy harvesting technique, the voltage obtained from a harvesting power source is as low as 0.1 V to 0.2 V. Thus, in order to drive a microcomputer or the like, it is necessary to boost the supply voltage applied to a load circuit up to approximately 1 V using a booster circuit. Here, in the case of a switching regulator which uses an inductor, for example, a control voltage of approximately 0.6 V or higher is required to boost 0.1 V to 1.0 V. Thus, to realize a so-called cold-start, that is, a boosting operation from an initial voltage state of 0 V, it is necessary to generate a high potential using a transformer or a charge pump circuit. Among these devices, the charge pump circuit which does not require an external device to be attached thereto and is not expensive has approximately several to ten stages. When a NMOS transistor of which the substrate potential is fixed to 0 V (the ground voltage GND) is diode-connected to form a charge pump, a reverse substrate bias is applied as it proceeds to the subsequent stages. Thus, the performance (boosting potential and current feeding ability) of the charge pump circuit deteriorates. Japanese Unexamined Patent Application Publication No. 2005-333685 discloses an example of a charge pump circuit driven on the basis of low-voltage.
The charge pump circuit disclosed in Japanese Unexamined Patent Application Publication No. 2005-333685 includes a substrate-control MOS transistor that switches a supply source of a back-gate voltage so that the back-gate voltage of a PMOS transistor (transfer MOS transistor) serving as a rectifying device is supplied from a terminal having the higher voltage among the source and drain terminals.